LANDSCAPE

COOL-SEASON TURF DISEASES

Integrating new ideas and new tools with accepted knowledge and fungicides is the key to successful cool-season disease management.

by Dr. Bill Shane, Ph.D., Ohio State University

Cool-season turfgrass managers face a wide variety of diseases that reduce the quality of their

grass. Choosing the proper strategies for managing these diseases depends greatly on being able to identify the disease.

Attention has centered recently on the subject of turfgrass patch diseases. Although much has been learned, confusion still remains in the minds of many turf managers when it comes to determining the cause of patches in their own situation.

This article will focus on the patho-gens that infect primarily basal stem, crown and root tissues of plants. The diseases discussed here are summer patch, necrotic ring spot, take-all patch and yellow patch diseases of cool-season turfgrass.

Other diseases associated with patch symptoms, (brown patch, Pythium blight, copper spot) are pri-marily leaf, sheath, and basal stem problems.

A recent challenge to turf mana-gers is determining the proper way to use the relatively new group of fungicides known as the sterol bio-synthesis inhibitor compounds (SBI) ( t r i ad imefon , f enar imo l , pro-piconizole).

Another new development is the availability of turf disease diagnostic kits. This is a rapid means to deter-mine the cause of turf decline, but it requires some new thinking to use the tool properly.

As more information is gathered about patch diseases, it is becoming clear that not all patch diseases are prevalent in all areas where cool-sea-son turfgrasses are grown. Necrotic ring spot has been common on Ken-tucky bluegrass in Washington, Colo-rado, New York, Wisconsin, and Minnesota but less common in Penn-sylvania, Maryland and Ohio.

This disease may be prominent for a few years in a region but then be-come obscure. For example, necrotic

r ing spot b e c a m e ve ry sca rce in Wisconsin during the summer of 1988, according to Dr. Gayle Worf of the University of Wisconsin.

Summer patch Summer patch, caused by the fungus Magnaporthe poae, is common in Kentucky bluegrass in Rhode Island, Maryland, New Jersey and New York, but apparently less so in other areas of the country. The region of the United States where summer patch is impor-tant is somewhat wider for the annual bluegrass form of the disease.

The disease has a fairly distinctive appearance on close-cut annual blue-grass/bentgrass greens. The annual bluegrass is affected whereas the bentgrass is essentially untouched.

Unfortunately, summer patch is difficult to distinguish from necrotic ring spot on Kentucky bluegrass. The most useful characteristic to dis-tinguish the two diseases is that spots of summer patch on Kentucky blue-

Summer patch symptoms on an annual bluegrass/ bentgrass green. Only the annual bluegrass plants are affected.

Rings on Kentucky bluegrass in a lawn due to yellow patch, which is caused by Rhizoctonia cerealis. Photos courtesy of Dr. Shane.

MANAGEMENT

COOL-SEASON TURF DISEASES, TURF DISEASE AND CONTROLS

DISEASE

SEASON AND/OR SUSCEPTIBLE TURFGRASS2 CULTURAL

FUNGICIDE/NEMATICIDE ACTIVE INGREDIENT4

Algae All tufgrasses Reduce shade. Avoid excessive fertilization. Improve soil drainage.

Mancozeb

Anthracnose (Colletotrichum graminicola)

July-August; ANNUAL BLUEGRASS, BENTGRASS; Fine Fescue

Fertilize and water to maintain vigor. Syringing may help to prevent stress.

Benomyl3, Triadimefon Thiophanate-Methyl3

Propiconizol, Fenarimol, Chlorothalonil

Brown Patch - See Rhizoctonia Wight

Dollar Spot (Lanzia and Moellerodiscus spp., formerly Sclerotinia homeocarpa)

Late June-Oct. BENTGRASSES BLUEGRASSES Fescues Ryegrasses

Avoid nitrogen deficiency. Remove dew from greens by mowing, dragging with a hose or pole. Choose more resistant grass varieties.

Chlorothalonil, Cadmium3, Benomyl3, Anilizine3, Fenarimol, Iprodione3, Propiconizol, Thiophanate- ethyl3, Thiophanate-methyl3, Thiram, Triadimefon, Vinclosolin3

Fairy Rings (Basiodomycete soil fungi)

April-October All turfgrasses

Remove infested sod and soil, replace with clean soil and reseed or sod. Improve water penetration. Increase N fertilization.

Methyl bromide or Formaldehyde fumigation will eradicate fungus but will also kill turf

Fusarium Blight5

8Fusarium poae, vulmorum,

F. crookwellense)

July-August Bluegrasses Bentgrasses Fescues

Reduce heat stress during dry periods by light, frequent watering. Do not cut Kentucky bluegrass ro fescues under 2 inches. Reduce excessive thatch (over % inch).

Triadimefon, Fenarimol Benomyl3, Iprodione, Thiophanate-methyl3, Thiophanate-ethyl3

Fusarium Patch (Pink Snow Mold) (Fusarium nivale)

Nov.-April Bluegrasses Bentgrasses Fescues Ryegrasses

Avoid late fall fertilizing. Rake leaves and cut short. Control drifting snow.

Triadimefon, Benomyl3, Fenarimol, Iprodione3, Mancozeb, Mercury chlorides, Pentachloronitrobenzene, Thiram, Thiophanate-methyl3, Vinclozolin

Grey Snow Mold- see Typhula blight

Leafspot/Blight /Melting out (Drechslera & Bipolaris ssp.)

Leafspot: Spring & fall; Blight & Melting out: June-Aug. KENTUCKY BLUEGRASS BENTGRASSES FINE FESCUE, ryegrasses, tall fescue

Remove clippings. Raise cutting height. Avoid excessive nitrogen. Avoid light, frequent watering.

Cycloheximide, Iprodione, Chlorothalonil, Mameb, Nancozeb, Vinclozolin, Pentachloronitrobenzene

Nematodes All turfgrasses Fenamiphos, Ethoprop

grass tend to remain small (3 to 10

inches in diameter) compared to nec-

rotic ring spot (5 inches to 2 feet).

Unt i l recently, ident i f icat ion of

summer patch by plant disease clinics

has been hampered; the causal fungus

displays no consistent distinguishing

features when grown on agar in a petri

plate.

Formerly, the causal agent was

thought to be the fungus Phialophora graminicoJa. This was a major source

of confusion to plant pathologists be-

cause this fungus was known to be a

non-pathogen on cereal crops.

A breakthrough A major advance in our understand-

ing of summer patch occurred when

Peter Landschoot (now at Pennsyl-

vania State University) and Noel Jack-

son (Un ivers i ty of Rhode Is land)

discovered that there are two mating

types, 'A' and 4a\ for the causal agent

now known as Magnaporthe poae. If a

suspected M. poae strain is paired

with the proper mating type, the sex-

ual spore stage (ascospores) is formed

and posit ive ident i f icat ion can be

made. Thus, identification of summer

patch is now possible, but still takes

up to two months.

Yellow patch Yellow patch, caused by Rhizoctonia

cereaJis, is frequently found on Ken-

tucky bluegrass in Oh io and appar-

ently less frequently in Michigan and

I l l i no i s . It is rare ly reported in

W i s c o n s i n a n d M i n n e s o t a . The

bentgrass version of the disease is

more often seen in the nor thern

TABLE 1. TURF DISEASE

COOL-SEASON TURF DISEASES, TURF DISEASE AND CONTROLS

DISEASE*

SEASON AND/OR SUSCEPTIBLE TURFGRASS2 CULTURAL

FUNGICIDE/NEMATICIDE ACTIVE INGREDIENT4

Necrotic Ring Spot5

(Leptosphaeria korrae)

Spring & fall KENTUCKY BLUEGRASS, annual bluegrass ryegrasses

Avoid low mowing heights (below 2 inches). Reduce excessive thatch (over % inch). Use Kentucky bluegrass and perennial ryegrass mixtures.

Fenarimol, Propiconizol

Pink Patch6

(Limonomyces roseipellis)

Spring & fall bentgrass, FINE FESCUE, PERENNIAL RYEGRASS

Follow balanced fertilization program.

Cadmium, Mancozeb

Pink Snow Mold - see Fusarium patch

Powdery Mildew (Erysiphe graminis)

July-Oct. KENTUCKY BLUEGRASS, fine fescue

Reduce shade. Increase air circulation by removing surrounding vegetation.

Triadimefon, Fenarimol, Propiconizol

Pythium Blight (Pythium aphanidermatum, P. graminicola)

June-Sept. BENTGRASSES, ANNUAL BLUEGRASS, PERENNIAL RYEGRASS, Kentucky bluegrass

Improve soil drainage. Increase air circulation by removing surroundign vegetation. Avoid mowing wet grass. Avoid excess watering.

Chloroneb, Etridiazole, Propamocarb, Metalaxyl, Fosetyl-AI, Mancozeb

Red Leaf Spot (Drechslera erythrospila)

June-Sept. BENTGRASSES

Remove clippings. Fertilize to maintain vigor.

Iprodione, Anilizine

Red Thread (Laetisaria fuciformis)

All seasons PERENNIAL RYEGRASS, FINE FESCUE, bentgrass, annaul bluegrass, Kentucky bluegrass

Follow balanced fertilization program.

Vinclozolin, Cadmium, Chlorothalonil, Thiophanate-ethyl, Thiophanate-methyl, Nancozeb, Triadimefon Propiconizole

Rhizoctonia Blight (Brown patch) (Rhizoctonia solani = Thanatephorus J cucumeris)7

July-August BENTGRASS, ANNUAL BLUEGRASS, TALL FESCUE, Kentucky bluegrass, fine fescue

Avoid excess nitrogen fertilization. Increase air circulation, by removing surrounding vegetation. Avoid excessive watering.

Anilizine, Chlorthalonil, Mancozeb, Benomyl3 Maneb, Propiconizole, Pentachloronitrobenzene, Triadimefon, Thiophanate-methyl3, Thiophanate-ethyl3, Iprodione

Rust (Puccin ia spp.)

August-Oct. PERENNIAL RYEGRASS, KENTUCKY BLUEGRASS

Avoid nitrogen deficiency. Use resistant varieties of Kentucky bluegrass and perennial ryegrass.

Mancozeb, Propiconizole, Cycloheximide, Chlorothalonil, Triadimefon, Fenarimol

Slime Molds (Myxomycete9

August-Sept. All Turfgrasses

Removing mechanically by mowing or raking.

Zineb, Mancozeb

Snow Mold - see Fusarium Patch and Typhyula Blight

United States and Canada. T w o features are useful in dis-

tinguishing yellow patch from nec-rotic ring spot and s u m m e r patch. Plants suffering from yellow patch display a white, shredded appearance of the basal stem tissue. In addition, leaf spots somewhat reminiscent of dollar spot are sometimes present on the portion of the leaf blade closest to the leaf sheath.

Yellow patch is generally a less se-vere disease problem than s u m m e r patch and necrotic ring spot but will on occasion cause unsightly patches and scars on Kentucky bluegrass turf.

Take-all patch T a k e - a l l p a t c h , a l s o k n o w n as O p h i o b o l u s or G a e u m a n n o m y c e s p a t c h , is p r i m a r i l y r e s t r i c t e d to bentgrass. It is most common to the

P a c i f i c N o r t h w e s t , N o r t h e a s t and mid-Atlantic regions of the country. It has been reported less frequently in other states such as Wisconsin, Pen-nsylvania, Michigan and Ohio.

T h e key for identifying this disease is to watch for it on newly-establ ished greens, especially those greens with high soil pH ( > 7). It is also primarily a problem only on bentgrass.

Why these various patch diseases

TURF DISEASE

DISEASE

T A B L E 1 C O O L - S E A S O N T U R F DISEASES, T U R F DISEASE A N D C O N T R O L S

DISEASE

Strip Smut (Ustilago striiformis)

Summer Patch5

(Magnaporthe ssp., formerly Phiaophora graminicola)

Take-all Patch (Ophiobolus patch) (gaeumannomyces gram in is var a venae)

SEASON AND/OR SUSCEPTIBLE TURFGRASS2

Spring & fall KENTUCKY BLUEGRASS, Bentgrasses

June-August ANNUAL BLUEGRASS, KENTUCKY BLUEGRASS

Spring & fall BENTGRASS

CULTURAL

Avoid drought stress. Avoid excess nitrogen.

Avoid low mowing height. Reduce excessive thatch. Light, frequent watering during dry periods to reduce heat stress. Use slow-release nitrogen to avoid nutrient depletion. Use Kentucky bluegrass and perennial ryegrass mix.

Avoid topdressing soil with pH greater than 6.0 Avoid use of lime, especially small particle type, where take-all is a problem. Use ammonium chloride, or second best, ammonium sulfate fertilizers.

FUNGICIDE/NEMATICIDE ACTIVE INGREDIENT4

Propiconizole, Triadimefon, Benomyl, Thiophanate-ethyl Notes. Apply extra water for crown penetration. Apply in late fall or early spring

Fenarimol, Triadimefon; Materials must be applied preventatively.

PMA (not labelled for this disease, but may be effective)

Typhula Blight (Grey Snow Mold) (Typhula spp.)

Nov.-April fine fescue, BENTGRASS, ANNUAL BLUEGRASS, Kentucky bluegrass, tall fescue, perennial ryegrass

Avoid heavy fall nitrogen promoting late lush growth. Rake leaves and cut short. Control drifting snow.

Triadimefon, Cadmium, Chloroneb, Anilizine, Pentachloronitrobenzene, Mercury Chlorides, Thiram

Yellow Patch (Rhizoctonia cerealis)

Spring & fall Bentgrasses Bluegrasses

Reduce excessive thatch. Avoid excessive watering.

None

Yellow Tuft (Downy mildew) (Sclerophthora spp.)

Spring & fall Bentgrass

Metalaxyl

1 Before using any pesticide, read and follow all label instructions. 2 Grass types listed in capital letters have been observed to be especially susceptible to the pathogen. 3 Continued or sole use of these materials may favor build-up or resistant fungal population 4 Products containing these active ingredients are listed in the following table. Read the product label to see if it is labelled for the disease of concern. Follow all label instructions. 5 Necrotic ring spot ans summer patch are known to cause symptoms once attributed solely to Fusarium blight. 6 Pirik patch disease was recently found to be a disease distinct from red thread. Thus, there are few fungicides specifically registered for contorl of this disease at this time. 7 Anothe fungus. Rhizoctonia zeae, is also capable of causing brown patch-like symptoms on bluegrass and bentgrass. Benzimidazole type (Tersan 1991, Benomyl. Fungo 50. Clery 3336) are not effective against this pathogen.

Source: Dr Shane

a re p r e v a l e n t in d i f f e r en t r eg ions of t h e c o u n t r y is s t i l l u n c l e a r . M o s t l i ke ly r e a s o n s a r e t h e r e s u l t of cl i-m a t i c d i f f e r e n c e s a n d b e c a u s e t h e c a u s a l f u n g i h a v e no t s p r e a d to all c o o l - w e a t h e r tur f g r o w i n g a reas .

O u r p i c t u r e of t h e d i seases in e a c h reg ion of t h e c o u n t r y is stil l f r a g m e n -tary , largely b e c a u s e t h e d i seases a re di f f icul t to i d e n t i f y in t h e field a n d l abora to ry .

A n exc i t i ng d e v e l o p m e n t for t h e t u r fg ra s s d i sease i n d u s t r y h a s b e e n a

n e w class of f u n g i c i d e s co l lec t ive ly k n o w n as t h e s terol b io syn thes i s - i n -h i b i t i n g f u n g i c i d e s (SBI) (T ab l e 3). T h r e e a r e c u r r e n t l y l a b e l l e d f o r t u r fg ra s s d i seases , a n d m o r e a r e b e i n g d e v e l o p e d .

W e l c o m e SBI fungicides Most f u n g i a t t a c k i n g turf s y n t h e s i z e ergos tero l , a s te ro l u s e d in t h e i r cel l m e m b r a n e s . T h e SBI f u n g i c i d e s con-trol m a n y f u n g i by b l o c k i n g t h e syn-thes i s of e rgos tero l . For th i s r eason , an

a l t e r n a t e n a m e , e r g o s t e r o l b i o -s y n t h e s i s i n h i b i t o r s (EBI), is s o m e -t i m e s u s e d . F u n g i , s u c h a s t h o s e c a u s i n g P y t h i u m b l igh t a n d d o w n y m i l d e w t h a t d o n o t m a n u f a c t u r e ergos terol , a re not con t ro l l ed by these fung i c ide s .

SBI f u n g i c i d e s a re sys temic . T h e y h a v e a r a t h e r b r o a d s p e c t r u m of act iv-i ty, a l t h o u g h no t as b r o a d as ch lo-r o t h a l o n i l o r m a n c o z e b ( T a b l e 4). Most SBI f u n g i c i d e s do not h a v e good p r o t e c t a n t ac t ion b u t r a t h e r w o r k best

TABLE 1. TURF

Table 2.

FUNGICIDE DIRECTORY

TRADE NAMES OF TURFGRASS FUNGICIDES AND NEMATICIDES

Active Ingredient

FUNGICIDES Anilizine

Anilizine + maneb w / zinc

Benomyl

Cadmium chloride Cadmium chloride -I- thiram

Cadmium chloride -I- thiram 4- zineb

Cadmium sebacate + thiram + potassium chromate

Cadmium succinate Chloroneb Chlorothalonil Cycloheximide Cycloheximide + PCNB Cycloheximide + thiram Ethazol (etridiazole) Fenarimol Fosetyl-AI Iprodione Mancozeb

Maneb Maneb + zinc sulfate

Mercury chloride Metalaxyl Pentachloronitrobenzene

(PCNB, quintozene) Phenylmercuric acetate Phenylmercuric acetate

+ thiram Propamocarb Propiconizol Thiabendazole Thiophanate-ethyl Thiophanate-ethyl + thiram Thiophanate-methyl

Thiophanate-methyl + mancozeb

Thiophanate + iprodione

Thiram Triadimefon

Triadimefon -I- metalaxyl Triadimefon + thiram Vinclozolin Zineb

NEMATICIDES Ethoprop Fenamiphos

Some Common Trade Names1

Lofts Dyrene, Lescorene, Proturf Fungicide Lawn Fungicide Faesy & Besthoff Lawn and Turf Fungicide

Tersan 1991, Rockland Benomyl, Lebanon Fungicide Type B Caddy Dexol Thiram Plus Lawn Fungicide, Lesco Snow Mold Turf Fungicide, Clearys Granular Turf Fungicide, Cleary s Cad-Trete, Lebanon Fungicide Type T Bonide Lawn Fungicide

Kromad

Cadminate Tersan SP, Teremec SP, Proturf Fungicide II Daconil 2787, Lebanon Fungicide Type D Acti-dione TGF Acti-dione RZ Acti-dione Thiram Koban, Terrazole Rubigan Aliette Chipco 26019, Proturf Fungicide VI Fore, Formec, Dithane M-45, Dithane F-45, Lesco 4, Manzate 200 DF Dithane FZ, Dithane M-22 Tersan LSR, Dithane M-22 w/Zinc, Lesco 4 F w/Zinc Calo-chlor, Calo-gran Subdue, Proturf Pythium Control Terraclor, Turfcide, Lawn Disease Preventor, Lesco PCNB PMAS Proturf Broad Spectrum Fungicide, 24-5-3 Fertilizer Plus Fungicide Banol Banner Tobaz, Mertect 140F Cleary s 3336 F, Cleary s 3336 WP Bromosan WP, Bromosan F Fungo 50, Spot-Kleen, Topsin M, Proturf Systemic Fungicide Duosan

Proturf Fluid Fungicide, Disease Control Plus Fertilizer 23-3-3 Tersan 75, Spotrete, Thiramad Bayleton, Proturf Fungicide 7, Lebanon Turf Fungicide Proturf Fluid Fungicide II Proturf Fluid Fungicide III Vorlan Zineb

Mocap Nemacur

Source: Dr Shane

iMany products may be available only through specialized dealers or only in large quantity. Some products can be purchased and applied only by licensed pesticide applicators. This list is presented for information only. No endorsement is intended for products mentioned, or is criticism meant for products not mentioned.

systemically. SBI fungicides are par-ticularly effective against powdery mildew, rusts and stripe smut.

Jury still out Information is still incomplete for the activity of these fungicides against the slow-growing root and crown diseases necrotic ring spot, summer patch and yellow patch. Current opinions are that f ena r imo l and possibly pro-p i c o n i z o l e p r o v i d e good ac t i on against necrotic ring spot.

Triadimefon is reported to have ac-tion against summer patch; effec-t i v e n e s s of f e n a r i m o l a n d pro-piconizole against this disease is not clear.

With all these patch diseases it is important to apply the fungicides be-fore the symptoms appear. No chemi-cal has been shown to be effective against yellow patch in the field.

Fungicide resistance Resistance of fungi to fungicides is a constant threat, especially those with systemic action. Resistance of fungi to MBC-releasing fungicides (benomyl, me thy l - and e thyl - th iophana te ) , acylalanine (metalaxyl), and ipro-dione and vinclozolin fungicides has occurred where the compounds have been used frequently.

Resistance of turf disease fungi to SBI fungicides has not yet been re-ported. Resistance to SBI has been noted for other systems such as apple scab on apples and powdery mildew on ornamental plants.

It is prudent to assume that resis-tance to SBI fungicides can and will occur with turfgrass diseases.

Although it appears that a variety of SBI fungicides can be chosen, in actuality all the products being devel-oped for turf have the same mode of action. If a fungus develops resistance to one, it will have resistance to them all.

With most fungicides the appear-ance of resistance is "all or noth-ing"—meaning that a fungus with resistance is able to tolerate very high concentrations of the fungicide.

With SBI fungicides, resistance is cumulative; meaning the fungus can still be controlled (for a while) at a higher fungicide dose. As a result, re-sistance of fungi to SBI fungicides will be more difficult to detect because the fungicides will still control the patho-gen, although less satisfactorily.

Basic rules apply As with any fungicide, it is important to switch or tank mix fungicides with different modes of action to delay or avoid resistance build-up.

Another well-documented effect

TABLE 3.

FUNGICIDE DIRECTORY

Sterol biosynthesis-inhibiting fungicides labelled for or being developed for turfgrass disease control.

ACTIVE INGREDIENT

LABELLED

fenarimol

triadimefon

propiconizole

TRADE NAME

Rubigan

Bayleton

Banner

OTHER NAME

Tilt

COMPANY

Elanco

Mobay

Ciba Geigy

CHEMICAL CLASS

pyrimidine

triazole

triazole

EXPERIMENTAL penconazole

prochloraz

flusilazol

Spotless Lynx

Nustar

HWG 1608 Uniroyal Mobay

Noram

DuPont

triazole imidazole

imidazole

triazole

Source: Or. Shane

TABLE 4.

FUNGICIDE DIRECTORY

Activity of sterol biosynthesis inhibiting fungicides against selected diseases of turfgrass.

ACTIVITY DISEASES

poor leaf spot (Drechslera and Bipolaris species)

fair to good brown patch (Rhizoctonia solani) anthracnose (Colletotrichum graminicola)

good to excellent rust (Puccinia species) powdery mildew (Erysiphe species) stripe smut (Ustilago striiformis) dollar spot (Lanzia and Moellerodiscus species)

of SBI fungicides is their growth-reg-ulating effect on the turfgrass plant. High rates of fenarimol can depress Poa a n n u a g r o w t h . S o m e SBI fungicides may induce a noticeable greening of other grass species.

There are some indications that high rates of SBI fungicides may in some instances slightly retard the growth of grass types other than Poa annua. This is not detrimental except in cases where vigorous growth of turf is desirable; for example, if leaf pro-duction is needed to fill out a poor grass stand.

Disease detection kits A new approach has been developed for the age-old problem of identifying

Sourc*: Dr Shane

turf diseases. Antibodies—tiny pro-teins in the immune system of mam-mals—allow the recognit ion and neutralization of invading pathogens.

With current technology it is possi-ble to produce antibodies to recognize turf pathogens for diagnostic pur-poses. With this approach a small sample of leaves suspected of harbor-ing a plant pathogen is ground. The sap is then tested for the proteins or carbohydrates specific to the patho-gen.

Agri-Diagnostics and Associates (Cinnaminson, NJ 08077) has devel-oped a kit (Reveal) that positively identifies dollar spot, warm-weather Pythium blight, and brown patch in 10 minutes.

An innovative feature of the Re-veal kit is that positive and negative controls are included with each test to insure that it is done correctly.

More kits to come Antibody-based diagnostic tests for other turf diseases such as necrotic ring spot and summer patch are being deve loped in o ther laborator ies . These kits allow disease problems to be quickly identified so that proper selection of fungicides can be made.

A knowledgeable turf manager can identify most common turf diseases when the symptoms are typical. How-ever, even the most careful observer can be mislead when disease symp-toms and signs are atypical or non-defini t ive. For example, mycelial growth on tall-cut grass can be due to Py th ium blight, brown patch, or Nigrospora blight.

As with traditional methods for di-agnosing disease, the quality of the grass sample collected for diagnosis is important for successful use of anti-body-based techniques. The pathogen responsible for a patch symptom on a grass stand will usually decline to un-detectable levels within a few days of symptom expression.

Note kit selectivity It is also important to know the se-l ec t i v i t y of t he t e s t s u sed . For example, the Agri-Diagnostic test for brown patch used in 1988 was specific for Rhizoctonia solani and did not re-act to most isolates of Rhizoctonia zeae, a fungus that also may cause brown patch symptoms.

The antibody kits will react against living and non-living forms of the tar-get fungus. Some turf managers may use the kits to see if a fungicide appli-cation was effectively stopping a dis-ease epidemic. However, sufficient time must be given for a fungicide to act and the fungal population to de-cline through mowing and deteriora-tion before the grass is tested again. Experience has shown that 2 or 3 days are needed to see the results of a fungicide application with the anti-body kits.

An attractive aspect of antibody-based diagnostic kits is that the turf manager can in some instances very quickly determine (or at least rule out) one possible cause of a turf problem.

Costs for the diagnostic kits may be an issue, especially for lawn care com-panies and diagnostic clinics. Current costs for the rapid assay format of the Agri-Diagnostic kits is more than $15 per test. The kits may be economical for golf course settings, in situations where lawsuits may be pending, or for special customer-relation cases. LM